1. Field of the Invention
The present invention relates to fluoroalkyl-functional organopolysiloxane-containing compositions based on alcohol, to a process for their preparation and to their use.
2. Description of the Background
Organosilanes of the formula R'-Si(R").sub.3, where R' is a fluorinated organic radical and R" is a chlorine or methoxy or ethoxy group, have diverse uses, for example, in the application of hydrophobically and oleophobically acting layers on surfaces. Such coatings and impregnations can be produced at the worksite, for example, by dipping, impregnating, spraying or rolling operations.
It is also known that oil- and water-repellent coatings on surfaces, usually glass surfaces, can be produced with fluoroalkylalkoxysilanes. The coatings can be used, for example, as a dirt-repellent treatment on plate glass. The processes described are based on sol-gel processes, very fine inorganic particles being produced and employed together with the fluoroalkylalkoxysilane. Application of such systems is technically demanding, and usually uses complex organic solvent mixtures and additives. Moreover, such systems comprise chlorine and furthermore only remain fit to use for a relatively short period of time (European Laid-Open Application No. 0 658 525, European Laid-Open Application No. 0 629 673 and U.S. Pat. No. 5,424,130).
Since the processes employed are sol-gel process embodiments, which are demanding both in their use and economically, their commercial utilization has to date been limited to niche areas. Furthermore, there are narrow time limits with respect to processability and, therefore, the subsequent efficacy of such fluoroalkylsilane containing formulations on a substrate surface. These factors are an impediment to broader use of the formulation in practice. In addition, a partial to complete loss of adhesive action can be experienced, and a slow phase separation up to laminar deposition of a fluoroalkylsilane-containing phase can occur.
The complicated application processes and, also the use of solvents such as fluorinated hydrocarbons or fluorohydrocarbons, therefore, are disadvantages of such processes (European Laid-Open Application No. 0 491 251, European Laid-Open Application No. 0 493 747).
In the case of the known solvent-based systems, it must be noted that although some systems are stable over the long term in the non-hydrolyzed state, they are distinguished by an efficacy limited to a maximum of a few days in the hydrolyzed form because of the progressive polycondensation of the silanol functions. When formulations are prepared in which the content of silanol groups is continuously reduced in order to reduce the undesired polycondensation, the extent of chemical bonding by the silanol groups to a substrate surface is furthermore reduced, this subsequently manifesting itself in unsatisfactory adhesion of the coating to the substrate surface. A need, therefore, continues to exist for an aqueous organosilane solution which is stable over prolonged periods of time and which provides coated substrates with both hydrophobic and oleophobic properties.